While many studies have shown that vision is altered and/or enhanced in deaf people, it is not known how this develops. The current proposal is the first to study visual development in deaf people from infancy to adulthood, as well as in hearing restored (HR) children who received cochlear implants (CIs) by 18 months, a cohort that is increasingly on the rise. In Aim 1, we measure different visual abilities (including motion, form, face and object perception) in deaf and hearing infants (6 - 10 months), children (6 - 10 years) and adults, using comparable stimuli/paradigms across ages. Many deaf people use a visual language, American Sign Language (ASL), and thus to tease apart whether altered vision in deaf signers is due to deafness or to experience with ASL, we test a third control group of hearing signers, who were born to deaf signing parents and have roughly the same ASL experience as deaf people who also learned ASL early. In infants, we test these same three analogous groups (sign-exposed deaf infants, non-sign-exposed hearing infants, and sign-exposed hearing infants), as well as an additional control group, i.e., non-sign-exposed deaf infants. To test the effects of ASL further, we ask whether the degree of altered vision correlates with receptive ASL proficiency, as measured with standardized ASL tests. By understanding the developmental trajectory of altered vision due to deafness vs. ASL, we hope to elucidate mechanisms of developmental plasticity. Aim 2 asks whether there is an early critical period for the effects of deafness on visual perception, by investigating whether altered vision persists in HR children. We also measure receptive spoken language proficiency in HR children, which allows us to ask by when in development must auditory input be restored for auditory and speech processing to develop normally. This aim also addresses a growing concern in the CI field that altered early vision in deaf people may hinder the efficacy of the CI. Here, the idea is that if deafness leads to functional reallocation of auditory cortex for visual processing, this might prevent the auditory cortex from being properly stimulated by CIs. If this is true, we expect to find that HR individuals with the most altered vision will show the worse proficiency in receptive spoken language. The current proposal will be the first to test this maladaptive hypothesis early in development, and the results should have implications for optimizing best long-term language outcomes in CI children.